Conventionally, for example, Japanese Patent No. 4992951B discloses a pneumatic tire having a designated tire front/back mounting direction when mounted on a vehicle. In the pneumatic tire, three main grooves extending in the tire circumferential direction are provided in the tread portion, the center position of the center main groove of the three main grooves is located in a position shifted away from the tire equator to the vehicle outer side, the length of shift d from the center position of the center main groove to the tire equator is in the range of 5% to 100% of the width L of the center main groove, four rows of land portions are defined by the main grooves, and one narrow groove extending in the tire circumferential direction and a plurality of inclined grooves extending from the narrow groove towards the outer side in the tire width direction are provided in each of the two rows of center land portions located on the tire equator side of the tread portion, the width of the center land portion on the vehicle outer side is greater than the width of the center land portion on the vehicle inner side, a plurality of lug grooves extending in the tire width direction is provided in each of the two rows of shoulder land portions located the shoulder sides of the tread portion, and these lug grooves do not connect to the main grooves.
According to the pneumatic tire of Japanese Patent No. 4992951B, it is possible to reduce the noise originating from the tread pattern by providing the three main grooves in the tread portion and by preventing the lug grooves in the shoulder land portions from connecting to the main grooves. Furthermore, the center position of the center main groove is located in a position shifted away from the tire equator towards the vehicle outer side, and the width of the center land portion on the vehicle outer side is greater than the width of the center land portion on the vehicle inner side. As a result, the main groove on the vehicle outer side is brought nearer to the ground contact edge. Therefore, the reduction effect of noise originating from the tread pattern can be enhanced.
Moreover, according to the pneumatic tire of Japanese Patent No. 4992951B, the center position of the center main groove is located in a position shifted away from the tire equator to the vehicle outer side, and the length of shift d from the center position of the center main groove to the tire equator is in the range of 5% to 100% of the width L of the center main groove, so it is possible to achieve both water drainage performance and noise performance at a high level.
The pneumatic tire according to Japanese Patent No. 4992951B as described above is disclosed, in which providing three main grooves in the tread portion and arranging the center main groove near the tire equator sometimes cause a reduction in steering stability. Therefore, in the pneumatic tire according to Japanese Patent No. 4992951B, the center portion including the center main groove and the outer portions located on both outer sides of the center portion in the tread portion are constituted of mutually different rubber compositions, and it is preferable that the hardness of the center portion be greater than the hardness of the outer portions. Thus, it is possible to maintain good steering stability while achieving both water drainage performance and noise performance.
However, in the pneumatic tire according to Japanese Patent No. 4992951B, the center position of the center main groove is located in a position shifted away from the tire equator to the vehicle outer side, so the width of the land portion on the vehicle outer side tends to be narrower. Therefore, turning or changing direction of traveling may cause a reduction in steering stability.